fuel cell = device that generates electricity by a chemical reaction.

Every fuel cell has two electrodes, one positive and one negative, called, respectively, the cathode and anode. The reactions that produce electricity take place at the electrodes.

-Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes.

Hydrogen is the basic fuel, but fuel cells also require oxygen. One great appeal of fuel cells is that they generate electricity with very little pollution much of the hydrogen and oxygen used in generating electricity ultimately combine to form a harmless byproduct, namely water.

-One detail of terminology: a single fuel cell generates a tiny amount of direct current (DC) electricity. In practice, many fuel cells are usually assembled into a stack. Cell or stack, the principles are the same.

INTRODUCTION

• Polymer exchange membrane fuel cell (PEMFC)

• Solid oxide fuel cell (SOFC)

• Alkaline fuel cell (AFC)

• Molten-carbonate fuel cell (MCFC)

• Direct-methanol fuel cell (DMFC)

• Phosphoric-acid fuel cell (PAFC)

Types of fuel cell

Polymer exchange membrane fuel cell (PEMFC)

for transportation applications. PEMFC has a high power density and a

relatively low operating temperature (ranging from 60 to 80 degrees Celsius, or 140 to 176 degrees Fahrenheit).

The low operating temperature means that it doesn't take very long for the fuel cell to warm up and begin generating electricity.

Solid oxide fuel cell (SOFC) for large-scale stationary power

generators operates at very high temperatures (between

700 and 1,000 degrees Celsius). This high temperature makes reliability a problem, because parts of the fuel cell can break down after cycling on and off repeatedly.

very stable when in continuous use. -In fact, the SOFC has demonstrated the longest

operating life of any fuel cell under certain operating conditions. The high temperature also has an advantage: the steam produced by the fuel cell can be channeled into turbines to generate more electricity. This process is called co-generation of heat and power (CHP) and it improves the overall efficiency of the system.

Alkaline fuel cell (AFC) This is one of the oldest designs for fuel

cells; the United States space program has used them since the 1960s.

The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized.

Molten-carbonate fuel cell (MCFC)

large stationary power generators. operate at 600 degrees Celsius, so they

can generate steam that can be used to generate more power.

have a lower operating temperature than solid oxide fuel cells, which means they don't need such exotic materials. This makes the design a little less expensive.

Direct-methanol fuel cell (DMFC) Methanol fuel cells are comparable to a

PEMFC in regards to operating temperature, but are not as efficient.

requires a relatively large amount of platinum to act as a catalyst, which makes these fuel cells expensive.

Phosphoric-acid fuel cell (PAFC) use in small stationary power-

generation systems. operates at a higher temperature than

polymer exchange membrane fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars.

spacecraft, rural locations, and in certain military applications

remote weather stations large parks in certain military applications Cell phone Vehicle Aviation

fuel cell propulsion system creates high-efficiency electrical power.

enable longer flight times, quieter operation, less heat signature, and higher reliability than batteries or other methods of propulsion for many UAV's.

Boeing developing a manned airplane powered only by a fuel cell and lightweight batteries.

using a Proton Exchange Membrane (PEM) fuel cell/lithium-ion battery hybrid system to power an electric motor, which is coupled to a conventional propeller.

The fuel cell provides all power for the cruise phase of flight. During takeoff and climb

Clean Energy with Environmental BenefitsFuel cells produce only heat and water as by-products.  

EfficientFuel cells extract more power from the same quantity of fuel than traditional combustion. The direct

electrochemical process reduces the amount of fuel consumed and leads to a 30% - 90% efficiency

depending on the fuel cell system and whether the heat by-product is utilized.

 

Complementary Technologies

Fuel cells work in conjunction with other technologies to offer a best-in-class solution and deliver

a significant environmental advantage.

Economic Business CaseMost businesses publicly support environmental protection and Green House Gases reductions.

CostChief among the problems associated with fuel cells is how expensive they are. Many of the component pieces of a fuel cell are costly.

Durability - Membranes cannot remain stable under cycling condition - Membranes tend to degrade while fuel cells cycle on and

off, particularly as operating temperatures rise. Hydration

Because fuel cell membranes must by hydrated in order to transfer hydrogen protons, fuel cell systems can’t continue to operate in sub-zero temperatures, low humidity environments and high operating temperatures.

Delivery -air compressor technologies currently available are not suitable for vehicle use, which makes designing a hydrogen fuel delivery system problematic.

Infrastructure-No infrastructure for hydrogen generation and delivery for commercial use.

Storage and Other Considerations-hydrogen storage considerations, vehicle weight and volume, cost, and safety.

-too large and heavy for use in standard vehicles.